Posts Tagged ‘solder’

Etch Factor

Sunday, February 10th, 2013

An etch factor or etch compensation is a process modification made by the Printed Circuit Board (PCB) manufacturer to compensate for the chemical etching process. The chemical etching process is a subtractive operation that removes copper gradually when forming the circuit pattern. The size of the features at the end of the process are smaller than the size of the features at the beginning of the process. When a PCB design requires a track width of 0.005″ (0.127 mm) the PCB manufacturer has to start out with a wider track. The amount the track is increased by is referred to as an etch factor or etch compensation. The etch factor is also proportional to the thickness of the copper or copper weight weight being removed. The more copper being etched through the larger the etch factor.

Etch factor added with CAM tool.

Etch factor added with CAM tool.

The fact that the PCB manufacturer has to increase the feature size to compensate for their manufacturing process is critical for a PCB designer to understand. The designer must provide enough spacing in their design for the PCB manufacturer to process the design. In other words, the minimum spacing in the design must meet the manufacturer’s minimum space that they may consistently process. In PCB manufacturing there are three types of spacing that we consider. They are… (more…)

Simple Yield Improvement. (Part 1)

Monday, December 31st, 2012

Over the past 15 years we have seen some very amazing advancements in technology. Our electronic devices have become smaller, faster and more powerful. The capabilities of these new devices have brought science fiction to life for many of us. What the common consumer does not realize is that these advancements have occurred in a more destructive Lead-Free assembly process. Lead Free assembly methods consisting of higher assembly temperatures (around 260ºC) for longer dwell times at temperature along with a smaller processing window for success. The assembly methods today are challenged to not only maintain yields but to improve them. All the while cutting costs where ever possible. The desire to cut cost is where we see the result of unintended consequences.

I have been asked repeatedly by customers for my opinion on methods to improve yields. I evaluate designs and work with designers and assemblers on solutions to help them improve yields. This includes in process and post process yields. In other words build it right the first time and make sure it lasts in the field. A common question I am asked by customers is…

What is the one thing that we can do that can  improve our yields?

The answer is very simple… (more…)

What damage does the assembly process do to a pcb? (part 6)

Wednesday, August 31st, 2011

In this final planned post of the “What damage does the assembly process do to a pcb?” series we shall discuss copper diffusion.

What is copper diffusion?

When soldering, copper diffusion is a process in which copper atoms are removed from the copper surface and redistributed into the solder over a wide area.

Back in 2005 I was running some thermal and solderability tests on multilayer boards using various types of cured laminates, different surface finishes and various solder alloys. I was doing my RoHS and Lead-Free due diligence. I had a whole range of tests that I was running. One test consisted of solder dipping a test board in 288°C solder for 20 – 5 second intervals. I was trying to make a multilayer board built on phenolic laminate delaminate. When I reached the tenth dip I had to stop my test. I didn’t make the board delaminate but I did dissolve away much of the copper circuitry into the solder pot. (more…)

What damage does the assembly process do to a pcb? (part 1)

Wednesday, August 17th, 2011

A colleague contacted me the other day with a topic that would make an excellent post on this blog.

“How can we solder boards with a Tg of 180°C or even 200°C at temperatures of 225-245°C without damaging the board?  Even with leaded boards the peak reflow temperatures are way above the board’s Tg.  How is this possible?”

The answer is simple. Every time a printed circuit board is exposed to soldering temperatures it becomes damaged. This is the case not only for Lead-Free soldering applications but also for eutectic soldering consisting of tin-lead.

Tg is one of several parameters to be aware of. In the case of Tg most designers refer to the value as (more…)